It is known to use additive manufacturing technology and techniques, together with fine polymer powders, to manufacture high-performance products having applications in various industries (e.g., aerospace, industrial, medical, etc.).
SLS is an additive manufacturing technique that uses electromagnetic radiation from a laser to selectively fuse a powder material typically having an average diameter of 25 to 150 μm into a desired 3-D object. The laser selectively fuses the powder material by scanning cross-sectional layers generated from a 3-D digital description of the desired object onto the top layer of a bed of the powder material. After a cross-sectional layer is scanned, the powder bed is lowered by one layer thickness in a z-axis direction, a new top layer of powder material is applied to the powder bed, and the powder bed is rescanned. This process is repeated until the object is completed. When completed, the object is formed in a “cake” of unfused powder material. The formed object is extracted from the cake. The powder material from the cake can be recovered, sieved, and used in a subsequent SLS process.
PEKK powders are of particular interest in the SLS process because objects that have been manufactured from PEKK powders are characterized by a low flammability, good biocompatibility, and a high resistance against hydrolysis and radiation. The thermal resistance at elevated temperatures as well as the chemical resistance distinguishes PEKK powders from ordinary plastic powders.
An SLS machine typically pre-heats the PEKK powder disposed on the powder bed to a temperature proximate to a melting point of the powder. Pre-heating the PEKK powder makes it easier for the laser to raise the temperature of PEKK powder to a fusing point, and inhibits unwanted distortions in formed objects during cooling. Techniques for pre-heating of PEKK powders are discussed, for example, in U.S. patent application Ser. No. 14/472,817, filed Aug. 29, 2014.
There is an ever-increasing need to manufacture objects via SLS using PEKK powders with improved strengths (e.g., improved tensile strengths in the z-axis direction), improved shape accuracies, and with fewer or no structural flaws (e.g., flaws due to improperly fused layers). Aspects of the present invention are directed to these and other problems.